/in/foo.cc: In function 'int main()':
/in/foo.cc:6:5: error: 'cout' was not declared in this scope
     cout"HelloWorld!"
     ^~~~
/in/foo.cc:6:5: note: suggested alternative:
In file included from /in/foo.cc:1:0:
/usr/include/c++/6/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^~~~